Contents

Introduction     1

Chapter 1: A Computer in the Making     5
Biographical Sketch     5
Defining His Task     6
Preliminary Decisions     8
Atanasoff's Elimination Algorithm     10
Original Storage Design     12
Vacuum-Tube Logic     18
The Memory     21
The Arithmetic Unit     23
Electronic Design of the Add-Subtract Mechanism     30
Timing and Control     46
Decimal Input-Output and Base Conversion     48
Intermediate Binary Input-Output     56
Computation Time     64

Chapter 2: Mauchly's Pre-Atanasoff Years     73
The Evidence     73
The Harmonic Analyzer     74
The Cipher Machine     85
The Two-Neon Device     87
Ring Counters     96
Plan for an Electronic Desk Calculator     99
The Situation as of December, 1940     102

Chapter 3: The ENIAC Connection     105
The ENIAC     105
The December, 1940, Meeting     114
The Interim Period     118
The Situation as of Early June, 1941     130
Mauchly's June, 1941, Visit to Iowa     133
The Post-Iowa Period     155
Mauchly's Testimony in an Earlier Suit     168
The Mauchly-Eckert Link      179
An Interpretation     181

Chapter 4: Atanasoff's Day in Court     195
The ENIAC Case     195
Atanasoff on the Stand     209
The Decision on Atanasoff     236

Chapter 5: Atanasoff's Place in History     257
A Technological Revolution     257
Atanasoff's Computer     264
The Causal Chain     271

Appendix A: Logic of Electronic Switching     293
Logic and Electronics     293
Atomic Switches     295
Compound Switches     299
Logical Structure of Adding and Subtracting Circuits     305
Atanasoff's Atomic Switches     311
Structure of Atanasoff's Add-Subtract Mechanism     320
Atanasoff's Place in the History of Computer Switching     326

Appendix B: Response to Kathleen Mauchly     355
Kathleen Mauchly's Advocacy      355
The Pre-Atanasoff Years     362
The Post-Atanasoff Years     371

References     379

Index     383